The present invention relates to a method for controlling rotation of a fixing roller which requires large torque at the time of starting and is used in an image forming apparatus such as an electrostatic copying apparatus or the like.
Japanese Unexamined Patent Publication No. 59-102265 discloses an electrostatic copying apparatus wherein a fixing roller is driven to prevent the fixing roller and a pressing roller from being fixedly connected with each other by toner at the common contact portion when the surface temperature of the fixing roller is lower to a stand-by temperature.
Japanese Unexamined Patent Publication No. 57-129476 discloses a fixing device of external heating type in which two driving sources are provided, int eh time of stand-by, a pressing roller and a fixing roller are not made in pressing contact with each other, the pressing roller and an external heating roller are driven by another driving source so that the fixing roller is prevented from being fixedly connected to the pressing roller.
Japanese Unexamined Patent Publication No. 63-214554 discloses an electrostatic copying apparatus wherein a high-speed main motor and a low-speed fixing motor are connected to a rotary shaft of a fixing roller through respective one-way clutches and the fixing motor is driven immediately before the main motor is started to lower a starting torque required for the main motor.
Since the conventional fixing roller has the period of suspension, the fixing roller and the pressing roller are fixedly connected by toner at the common contact portion. Consequently, greater starting torque is required at the time of starting the main monitor, so that a large amount of current flow or the driving of the main motor is delayed. The fixing device in which the fixing roller is made in non-contact with the pressing roller has a complicated structure.